Changing from one computer to another.

I've got a IBM 400mg computer and am wanting to change to a Intell 750mg. So what I did was change everything over into the Intell, then I booted it up to find that it did not want to go, it said something like this:

"Windows has stopped booting up because if it does so it could cause damage to the computer and it's content's(as in stuff on the hard drive)"

At first I thought I might have put my hard drive to close to a magnet and got it scrambled a bit but after I put it back into my old computer it worked fine. I was confused by this so I rang up my brother(who knows a lot about computers) and asked him about it, and he said that he had had the same problem and had to reinstall windows, something to do with windows not liking another motherboard as it had been installed on an IBM and was getting changed to a Intell. Anything to help would be great!